Romney didn't win it. McCain lost it:

Romney may not have won in Michigan so much as McCain lost it. And he lost it because of a characteristic tendency that makes him Romney’s opposite — political rigidity based on a sense of his own personal rectitude. Having said jobs in Michigan were not coming back, he went to Michigan and praised efforts to mandate an increase in fuel-mileage standards, which auto executives claim will raise the price of a car fully $6,000 — a job killer, in other words. And he spoke against drilling in the Alaska National Wildlife Refuge, which is the only realistic way for the United States to increase its own domestic oil supply.

McCain’s line is that he is a straight talker. But there are moments he seems to make a fetish of his own honesty, and asks others to support him solely because of it.